As shown in FIG. 1, a conventional LED driver IC 10 requires at least seven pins, including two capacitor pins CN and CP for a flying capacitor Cfly to be connected therebetween, a voltage input pin VIN to receive an input voltage Vi, a voltage output pin VOUT to connect to an output capacitor Cout to provide an output voltage Vo for driving an LED 12, a current output pin CS to connect to the LED 12 to provide a drive current Iout thereto, a dimming control pin EN to receive a dimming control signal GPIO to adjust the average value of the drive current Iout to thereby adjust the luminance of the LED 12, and a ground pin GND to connect to a ground terminal of the system. In order to reduce the pin count for cost reduction, U.S. Pat. No. 7,368,977 uses the capacitor pin CN to receive the dimming control signal GPIO and thus eliminates the dimming control pin EN. However, this art now can not satisfy the demands of users on LPC ICs.
Therefore, it is desired an LED driver IC with further reduced pin count.